Reaction vessels have long been provided with pre-incorporated reagents. Some have even been constructed so as to be stackable, one above the other, as shown in, e.g., U.S. Pat. No. 4,761,378. However, those stacked in the '378 patent are done so without the vessels actually nesting within each other.
On the other hand, it is known to actually nest reaction vessels within each other, as shown in a wet assay analyzer described in U.S. Pat. No. 4,260,581. However, these are nestable because there is no pre-incorporated reagent--the latter is added as a liquid during assay, column 3, lines 53-63.
In fact, nesting together reaction vessels with pre-incorporated reagent is especially difficult when more than 50% of the vessel height is nested in the adjacent vessel. The reason is that, unless care is taken, the vessel inside and above can mechanically wear off the reagent in the "outer" vessel below, especially during shipment and storage. The fact that more than 50% of the vessel height is nested increases this likelihood.